1OPTIPNG(1) General Commands Manual OPTIPNG(1)
2
6 OptiPNG - Advanced optimization program for Portable Network Graphics
7 (PNG)
8
10 optipng [-? | -h | -help]
11 optipng [options...] files...
12
14 OptiPNG is a PNG optimizer that recompresses image files to a smaller
15 size without losing any information. In addition, this program per‐
16 forms a suite of useful functions like integrity checks, meta-data
17 recovery and pixmap-to-PNG conversion.
18
20 The input files are image files of following types:
21 - Native format: PNG.
23 - External pixmap formats (currently supported: GIF, BMP, PNM and
25 TIFF).
26 OptiPNG processes each input file as follows:
28 - If it is a PNG file:
30 If it is possible to create an optimized version of the given
32 PNG file, the optimized file replaces the original one. The
33 original file can be backed up, at the user's option.
34 - Otherwise (i.e. if it is an external pixmap format):
36 An optimized PNG version of the given image file is created.
38 The output file name is created from the original file name and
39 the .png extension.
40 For example:
42 optipng file1.png file2.gif
44 will create an optimized file1.png and an optimized file2.png. (The
46 original file1.png is replaced by the optimized one; the original
47 file2.gif is left intact.)
48
50 Basic options
51 -?, -h, -help
52 Show a complete summary of options.
53 -o level
55 Select the optimization level.
56 Use -o0 to disable IDAT recompression trials.
57 Use -o1 to enable a single IDAT recompression trial.
58 Use a higher level to enable more trials (the higher the level,
59 the more trials).
60 The behavior and the default value of this user option may
61 change across different program versions. Use option -h to see
62 the details pertaining to your specific version.
63 -i type
65 Select the interlace type (0-1).
66 Use -i0 to produce a non-interlaced output.
67 Use -i1 to produce an interlaced (Adam7) output.
68 If this option is not used, the output will have the same inter‐
69 lace type as the input.
70 -k, -keep
72 Keep a backup of the modified file(s).
73 The files that use the backup names prior to the program execu‐
74 tion are not overwritten.
75 -q, -quiet
77 Run in quiet mode.
78 -v Run in verbose mode / Show copyright, version and build info.
80 Advanced options
82 -zc levels
83 Select the zlib compression levels.
84 The behavior and the default value of this user option may
85 change across different program versions. Use option -h to see
86 the details pertaining to your specific version.
87 -zm levels
89 Select the zlib memory levels.
90 The behavior and the default value of this user option may
91 change across different program versions. Use option -h to see
92 the details pertaining to your specific version.
93 -zs strategies
95 Select the zlib compression strategies.
96 The behavior and the default value of this user option may
97 change across different program versions. Use option -h to see
98 the details pertaining to your specific version.
99 -zw window size
101 Select the zlib window size (32k,16k,8k,4k,2k,1k,512,256).
102 The window size can be specified either in bytes (e.g. 16384) or
103 kilobytes (e.g. 16k).
104 -f filters
106 Select the PNG delta filters.
107 The behavior and the default value of this user option may
108 change across different program versions. The filter values 0,
109 1, 2, 3, 4 correspond to the PNG standard filters (None, Left,
110 Up, Average and Paeth, respectively). The other values are used
111 to specify adaptive filtering. Use option -h to see the details
112 pertaining to your specific version.
113 -nb Do not apply bit depth reduction.
115 -nc Do not apply color type reduction.
117 -np Do not apply palette reduction.
119 -nz Do not perform IDAT recompression (also disable reductions).
121 -fix Enable error recovery.
123 -force Write a new output file, even if it is larger than the input
125 file.
126 -full Produce a full report on IDAT. This option might slow down the
128 trials.
129 -preserve
131 Preserve file attributes (time stamps, file access rights, etc.)
132 where applicable.
133 -simulate
135 Run in simulation mode: perform the trials, but do not create
136 output files.
137 -out file
139 Write output file to file. The command line must not contain
140 more than one input file.
141 -dir directory
143 Write output file(s) to directory.
144 -log file
146 Log messages to file. For safety reasons, file must have the
147 extension .log.
148 -- Stop option switch parsing.
150 Notes
152 The option names are case-insensitive and can be abbreviated. Any
153 abbreviation must uniquely identify the full option name and must be no
154 shorter than two letters, unless one letter is explicitly permitted.
155 For example, -quiet can be abbreviated as -q or -qu (because -q is
156 explicitly mentioned in the list of possible options), while -preserve
157 can be abbreviated as -pr but not as -p.
158 Some options may have arguments that follow the option name, with or
160 without a whitespace used as a separator; e.g.
161 optipng -i1 -o3 file.png <=> optipng -i 1 -o 3 file.png
163 Range arguments are cumulative; e.g.
165 -f0 -f3-5 <=> -f0,3-5
167 -zs0 -zs1 -zs2-3 <=> -zs0,1,2,3 <=> -zs0-3
168 The zlib window size is automatically set to a minimum that does not
170 affect the compression ratio.
171 The output files will have all IDAT in a single chunk, even if no
173 recompression is performed.
174 Extremely exhaustive searches are not generally recommended.
176
178 optipng file.png
179 optipng -o5 file.png
181 optipng -o7 file.png
183 optipng -i1 -o7 -v -full -sim experiment.png -log experiment.log
185
187 Lossless image reductions are not completely implemented. (This does
188 NOT affect the integrity of the output files.) Here are the missing
189 pieces:
190 - The color palette reductions are implemented only partially.
192 - The bit depth reductions below 8, for grayscale images, are
193 not implemented yet.
194 - The gray(alpha)-to-palette reductions are not implemented yet.
195 BMP support is limited to uncompressed images.
197 TIFF support is limited to uncompressed, PNG-compatible (grayscale, RGB
199 and RGBA) images.
200 Metadata is not imported from the external image formats.
202
204 OptiPNG is written and maintained by Cosmin Truta.
205 This manual page was originally written by Nelson A. de Oliveira for
207 the Debian Project. It was later updated by Cosmin Truta, and is now
208 part of the OptiPNG distribution.
209OptiPNG Version 0.5.5 28 January 2007 OPTIPNG(1)